//https://leetcode.cn/problems/add-strings/

class Solution {
public:
    string addStrings(string num1, string num2) {
        int end1 = num1.size() - 1;
        int end2 = num2.size() - 1;
        int carry = 0;
        string strret;
        while (end1 >= 0 || end2 >= 0)
        {
            int val1 = end1 >= 0 ? num1[end1] - '0' : 0;
            int val2 = end2 >= 0 ? num2[end2] - '0' : 0;
            int sum = val1 + val2 + carry;

            carry = sum / 10;
            sum %= 10;

            strret += ('0' + sum);
            //strret.insert(strret.begin(),'0'+sum);

            end1--;
            end2--;
        }

        if (carry == 1)
        {
            strret += '1';
            //strret.insert(strret.begin(),'1');
        }

        reverse(strret.begin(), strret.end());

        return strret;

    }
};